This invention relates generally to high frequency RF/microwave bipolar power transistors and, more particularly, the invention relates to such a transistor having improved stability and gain and methods of fabricating the transistor.
Resistive emitter ballasting is typically used on large RF power bipolar transistors to avoid thermal runaway and to reduce the impact of processing nonuniformities on device characteristics. Unfortunately, the serial resistor in the emitter circuit results in reduced gain. Further, emitter ballast nonuniformities can result in RF performance variations.